This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-390963 filed Dec. 22, 2000, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a cooling device of electronic apparatus applicable to, for example, a personal computer, and particularly to a cooling device of electronic apparatus in which a noise generated by a cooling fan does not discomfort the user.
2. Description of the Related Art
In recent years, various types of electronic apparatus incorporating a CPU have been developed. As the performance of the CPU is improved, the latest electronic apparatus includes a cooling device to make full use of the performances of the CPU. Most of the cooling devices incorporated in this type of electronic apparatus adopt a so-called air-cooled system that lowers the temperature by rotating a cooling fan.
In the conventional cooling device utilizing the air-cooled system, in general, a desired temperature around the CPU is set by a target value setting unit. On the other hand, the temperature in a housing, which varies from moment to moment due to external perturbations, such as heat of the CPU, is detected by a temperature detecting unit. A control device controls the fan based on the desired temperature around the CPU set by the target value setting unit and the temperature detected by the temperature detecting unit. By the control of the control device, the temperature around the CPU is kept substantially the same as the set desired temperature around the CPU.
More specifically, for example, when the temperature detected by the temperature detecting unit is higher than the desired temperature around the CPU set by the target value setting unit, the fan is rotated at a predetermined rotation speed. When the detected temperature is lower than the desired temperature set by the target value setting unit, the fan is stopped in order to save power.
Conventionally, when the temperature around the CPU is higher than the desired temperature, the fan is immediately rotated at a predetermined speed from standstill. Thus, the fan, which has been completely silent, abruptly produces a noise.
This abrupt noise can acutely irritate the user. Thus, the fan necessary to make full use of the performances of the CPU discomforts the user.
An object of the present invention is to provide a cooling device of electronic apparatus in which a noise generated by a cooling fan does not discomfort the user.
To achieve the above object, the present invention may provide a cooling device of electronic apparatus comprising: a temperature sensor; a cooling fan; a noise detecting unit configured to detect a sound pressure of a noise generated by the cooling fan; and a fan control unit configured to control a rotation speed of the cooling fan based on a detection result of the temperature sensor and a detection result of the noise detecting unit.
In the above cooling device of electronic apparatus of the present invention, the cooling fan is controlled to increase the rotation speed gradually, so as not to cause a sudden rise of a noise that may acutely irritate the user. As a result, the noise generated by the cooling fan does not substantially discomfort the user.
When the temperature around the CPU is lower than the desired temperature, the cooling fan is controlled to decrease the rotation speed gradually. Consequently, the sudden fall of a noise that may acutely irritate the user is prevented.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.